Conventionally, as shown in FIG. 19, an electroless plating process was carried out by dipping a plural of plate-like works 10 housed in a rack R into processing solution Q accumulated in a tank (JP-A-2011032538). Here, unlike electroplating that an energization is carried out, electroless plating is a plating method that enable to plate merely by dipping a treatment object into the plating solution. By means of electroless plating, it is also possible to plate anon-conductor (insulators such as plastic, ceramics, etc.) as well.
A problem of dissolved oxygen in electroless plating or desmear process will be described. The existence of dissolved oxygen in the electroless copper plating solution causes a problem, because it leads to low precipitation of plating by the effect of restraining reaction between the electroless copper plating solution and a catalyst attaching to the work. Also, the existence of dissolved oxygen included in etching liquid used for desmear process causes a problem, because it leads to excessive etching on wetted part by the effect of promoting reaction of etching liquid to the work. For that reason, it is desirable to reduce an amount of the dissolved oxygen contained in the processing solution.
As shown in FIG. 20, there is the other plating apparatus, such as an electrolytic plating apparatus (JP-A-2006118019) which is attracting the plate-like work 10 into the processing solution Q smoothly by pouring the processing solution Q downwardly through a tapered aperture from above the tank V when the plate-like work 10 is falling into the tank V that comprises side walls W1, W2 proximally-positioned to the plate-like work 10. Also, there is the other plating apparatus, such as an electrolytic plating apparatus (JP-A-1997 (Hei09)031696) which is squirting the processing solution in a vertically upward toward the work that is held horizontally.